Human cytomegalovirus (CMV), like other members of the herpes viruses, has a propensity for the establishment of latent infections, CMV induces a wide variety of diseases i humans that usually occur in immunologically compromised individuals. In addition, CMV is associated with the acquired immune deficiency syndrome (AIDS) and with malignancies such as Kaposi's sarcoma. To fully understand the mechanisms which enable CMV to establish latent and persistant infections, it is necessary to obtain a better understanding of the molecular biology of CMV. Interaction of CMV with the human host can lead to the infection of two cell types, productive or non-productive. It is likely that the establishment of the latent state begins with the infection of a non-permissive cell which results in a limited expression of the genome. Infection of a non-permissive cell is characterized by the viruses inability to express the full complement of early and late genes in addition to being viral DNA negative. Because functional immediate early (IE) genes are necessary for early and late gene expression, it is likely that these IE genes play some critical role in latency. The IE genes are well characterized with respect to their location and structure but little is known concerning their functional role in CMV replication. Therefore, it is necessary to develop a better understanding of how these genes regulate CMV gene expression. This study will focus on analyzing the CMV regulatory proteins using both genetic and molecular analyses. To accomplish this goal several approaches will be used. 1) In Vitro DNA transfection systems will be developed to study the shift from IE to early CMV gene-expression. 2) Mutations will be constructed in specific regions of the IE genes and these mutations will be analyzed in in vitro transfection studies. 3) Conditionally lethal or temperature sensitive (ts) mutants will be generated using both random and localized mutagenesis. The ability of these mutated IE genes to positively or negatively regulate CMV gene expression will be addressed. A genetic analysis of these regulatory genes should lead to a better understanding of how CMV replication is regulated.